Glad you found some tips that resonated for you.
Different people respond well to different strategies. That first one is related to a philosophy I have adopted for myself - I think of it as "this is not the last donut you will ever see" though it isn't really about donuts. It's just about training myself not to always eat food because it's offered, even tasty treats.
For example, we have a nice breakfast at work every wednesday with bagels, pastries, waffles ... but the very fact that it is
every wednesday makes it quite easy to skip it. "Eh, I don't need that bagel today, I can get one next week." The same thing goes for many other treats - I can have a drink tomorrow, I can try the dessert next time. Very rarely am I presented with a truly unique opportunity to eat a treat, one that I can't pass up with the thought "some other time". It's good; it saves me from falling into the self-pity trap of "woe is me, I can never eat a slice of birthday cake again!" *sob* But then, I remember some folks on this board saying "next time" doesn't work for them - they have to tell themselves "never".
That second tip you mentioned works a little differently for me. I don't really want a small half cup scoop of ice-cream - I want a huge portion of ice cream. But it's easier not to eat any ice cream at all than to try to eat a small portion of it and then stop. I am so put off by fake imitation goodies that I'd rather eat no goodies at all than the pale substitutes. But, different people feel really differently about this one, I think. Some people swear by their substitutes, and that's great for them - but I'll pass.